I have no clue why i even bought a $350 desk top engraver? I think i was more curious than anything else to see what you get for such a low price. the short answer would be not a whole heck of a lot. So after playing with it and seeing the good bad and the ugly i decided to build one from scratch to expand on the things i liked.
The first thing that was a joke at best was the MDF top with no support in the mid work area. I had some light T- slot on the shelf so that got tossed on the original machine to make it a little bit useful for now. the material in general is way to light for any real kind of use and the stepper motors are far too small for any kind of cutting. So the only thing that is being kept is the spindle motor and mount. But the machine was built as a dual function machine and has the option to run a diode laser so after i finish the new frame the original machine will probably get a laser attached to it and get used for that. Over all the machine is laid out nice but to light for cutting anything other than aluminum dust .
what i do like is the spindle speed and the belt drives. Belt drives are not something i would want on everything but for light duty fast moving they are hard to beat. Once you get into the 10,000 rpm range you now are in the lower end of high speed machining and that is what i am interested in. i wanted a simple project for Linux cnc on top of all this since i have interest in the system so this was a good simple starter project to get my feet wet.
The original machine is lacking in top end travel speed but the acceleration is impressive with junk electronics. So i have some closed loop steppers that will give me the needed micro stepping to deal with a fast moving belt drive and give me the resolution needed.
just to toss some numbers out there. what i have can max out at around 2,100 IPM for a travel rate. i doubt a samll desk top can run that fast but my goal is to push it to the limit and see how far i can go.
here is a basic concept screen grab to give some more insight.
i made some custom belt clamps to also work as a tension system for the belt drives. just an example of what you can do with 3D milling on a machine like this. possible with a $350 machine but time intensive to say the least.
not very much to be honest. the motor mount and spindle and maybe some of the spindle electrical stuff under the hood. i took a quick look in the box and think it might be a BLDC running on 48V DC. it looks like it just turns on and off with a relay on the control board. i don’t think the GRBL boards run on anything more than 12V with the tiny steppers but i have not had time to really take a deep dive into everything yet.
the frame is made from the same extrusion that you would find on a 3D printer and as for deflection you can easily get 2mm of flex with little effort that’s not good even if you are engraving only. Tools tend to not like that
i was going to use some light extrusion i had on hand but decided to get some 15 series 1 sided t -slot. 15 series can use 5/16 or 8mm bolt. the other stuff i had on hand can only go up to 6mm for a bolt in the t-slot which is ok but bigger is better and the 1 sided t-slot is around 1/4 thinner on the overall height so i get some extra clearance.
it turns out bearing fits and keeping things concentric are too much to ask of a $350 machine. so i went to plan B and just stacked two bearings together with some washers as spacers where needed and things work really well now. i added some extra wiggle room for adjustment if needed and i am glad i did so i have one side working on the Y axis but have enough to share some more pictures.
well since things look pretty good for a rigid frame i decided to just go all in and get a proper high speed spindle so i bought a square frame 24,000 rpm spindle with some proper angular contact bearings and a ER 20 spindle so a 220V spindle and VFD will be driving it. $235 for both was not a bad deal.
Ok managed to keep all the belt tensioning to the outside of the travel area and will have 16 inches on the X axis and around 20.5 inches on the Y axis before limits are added so around 15.5 inches x 20 inches after the fact give or take. Everything seems to work really well and feels pretty good too so i decided to go all in and upgrade to a better spindle with some proper bearings and ER20 collets with some better numbers for light cuts and fast travel rates. after looking it seems to fit easy on what i have but i will be adding a second set of bearing trucks to the Z just to be safe.
Very interesting project you’ve got going. Keep the pictures coming. I think I have two 566 oz. closed loop steppers that I never used. Let me know if you are interested.
i might need something bigger on the Z axis but will give the 283 oz motor a try for now. this spindle is much bigger but the weight on the whole z axis is still probably only 15 lbs. i weighed the spindle and it came in at 10.2 lbs. it will fit nicely though.
a machine that can get up to 2,100 IMP and a spindle that can run at 24,000 RPM what could go wrong although the Z axis will not be that fast but still
3mm pitch 15mm width open ended. my first thoughts were gates belts until i priced them from gates. the open-ended belts are only sold in 50 ft lengths. prices were $14 to $15 per foot from gates. so, i got mine from overseas.
24 tooth drive pulley so 72mm of travel per revolution. this is why i went with a closed loop stepper system for the extra micro stepping. the price difference was so little i just got the encoder feedback for extra peace of mind. you need around 40k of micro stepping to get the resolution needed. you need the step counting speed of the drive as well to deal with all the micro stepping. the drives i have can do 500k per second so the system will max out at a 750 RPM range. in theory the machine can do around 2100 IMP max on the X and Y axis but that will be a lot slower based on frame limits. the Z will not be that crazy maybe 200 IMP but it is really short so it’s not that important. acceleration is probably more important on that end but tuning will dictate where that falls.
What a treat it was to get Linux CNC on a computer. for whatever reason it was i had a heck of a time getting through the installation. I think things are changing on how you go about installing Linux CNC. i ended up downloading Linux CNC directly after i made my bootable Linux media. Linux is pretty confusing to begin with just because you have so many variations of it.
i now have a basic machine finished minus the cable management and limits but done for the most part. the z axis had a few small things to button up and the table had to be attached. Now comes the fun part getting everything wired up but that part will be easy compared to getting things set up in Linux i think
Welli got my first signs of life under power today. the Machine does well running fairly fast but the computer i have hooked up is a bit old and seems to be the weak link as far as maxing out what the machine and electrical components can handle.
with a computer that is probably 15 years old i was able to do 700 IMP with some snap of the finger accelerations set. if i can get the latency down more and maybe get the timing set better maybe i can boost things a little more? one thing i found was cutting back on the micro stepping helped quite a bit on the acceleration. i need to test more i’m not sure how much multiple axis movement will factor into this but it’s still pretty quick and silky smooth on the movement so far
getting the network set and the computer talking with the mesa board was a bit of a chore but i got it going. then fighting with latency problem took some time to sort out as well. and then when i thought i had it all sorted out i could not get the motors to move it turns out the drivers have a dip switch to control the volage on the step and direction signals? so either i am getting old and forgetful or this is something new to me? i don’t ever recall seeing a 24V step and direction signal on anything i have done in the past? i figured it out but that had me scratching my head for a little bit
i dialed things in a bit and have my X and Y running at 800 IPM and got my Z running at 400 IPM now. i think that’s as good as it will get with the old computer. no warnings coming up in Linuxcnc so everything seems happy now.
when i get there i will let you see some video i just have to get some homing switched wired in and get some power to the spindle. i found my first issue on my Z axis this morning. the flex coupling flexes a little to much so i had to order a different style of coupler. i thought it was backlash at first but when i was doing some work i spotted the issue.
i have not moved the machine around to much with no drag chains. so getting those on was a must with the way this thing whips around i have had it up to 1200 IMP but i get warnings going that fast but don’t see anything obvious ?
one other issue was the bundle package on these stepper motors. the cables that came in the bundle were only 67" long and they were way to short by the time you run them through the drag chains. i got a longer set today and more stuff waiting to be delivered later this week. maybe some time over the weekend i can do an air cutting video if i can get it all back together by then
i have one side working on the Y axis but have enough to share some more pictures.
but that part will be easy compared to getting things set up in Linux i think 
